What is algae?
1. Microscopic plant that requires light for photosynthesis
- Uni-cellular or multi-cellular
- Motile or immotile
- At night, shifts from O2 production to consumption (respiration)
2. Thrives in the top 15–18” of the water column
3. Requires carbon dioxide (CO2) and bicarbonate ions (HCO3) to grow and reproduce
4. Algal activity can:
- Increase pH (note: above pH 8.5, H2S no longer creates odor issues
- Saturate the area below the air/water interface with up to 30 mg/L of dissolved oxygen
- Produce 1.6 lbs O2 per pound of algae on a typical summer day
There are two main varieties
- Creates a green appearance
- Generally beneficial and desirable in a facultative lagoon
- Indicates a healthy pond
- Caused by low pH/nutrient levels
- Can survive while higher animal forms (e.g. protozoa) consume the green algae
- Indicates a pond with issues
Algae is part of lagoon treatment
Problems algae causes
- Algae in effluent results in high TSS.
- Algae in the BOD5 sample bottle consumes O2 while incubating for 5 days, driving up the BOD5 test result.
- Seasonal die-off of algae contributes to solids accumulation. These solids are high in nutrients, such as ammonia and phosphorus, as algae assimilates these into its cell wall when it grows.
- Accumulation of dead algae in the sludge blanket can lead to feedback of nutrients when those solids break down anaerobically.
- Higher sludge levels reduce the depth of the lagoon, making it easier for algae to grow as sunlight can more easily penetrate the water column.
- O2 and pH both rise during the day and fall at night.
Solutions that treat the symptoms
- Chemicals: Chemicals like copper sulfate can be used to raise the level of toxicity in the water so algae cannot grow. Algae then die and sink to the bottom. Continual application is necessary to control algae.
- Covers: Lagoon covers eliminate sunlight and the opportunity for photosynthesis, preventing algae from growing.
- Ultrasonic: Ultrasonic emitters can either disrupt the algae’s cell wall, effectively killing it, or push the algae lower in the water column where it doesn’t get access to sunlight.
- Natural methods: Barley straw and grass carp can reduce algae.
Treat the cause
- Algae, like all plants, need nutrients to grow.
- Influent wastewater has nitrogen and phosphorus, which are fertilizer to the algae.
- Most of these nutrients are not treated in the lagoon and become part of the sludge blanket over time. Nutrients are contained in solids that settle and within the algae which dies off seasonally.
- Sludge buildup encourages algae to grow as sunlight can penetrate more easily to the bottom of a shallower lagoon, where algae form.
- In order to manage algae, you need to manage the sludge blanket.
More efficiency. More mixing.
In-situ sludge reduction
- Multiple sludge reduction studies have been conducted with dual action coarse and fine bubble technology utilized by the Ares.
- Simply by providing more mixing and oxygen to lagoons, sludge can be reduced in place.
- Average level of sludge reduction is 45–50%.
Related Blog Posts
Excess algae can disrupt wastewater lagoon treatment. Learn the options for prevention and removal.
Blue-green algae blooms in a wastewater lagoon interfere with treatment; nutrients in effluent can cause blooms in receiving waters.
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